Interlocking system for railroads



y 1939. J. VAUGHN INTERLOCKING SYSTEM FOR RAILROADS 2 Sheets-Sheet 1 Filed June 22, 1937 llllllllllllllllllllllllnlll AGE May 2, 1939. J. l. VAUGHN INTERLOCKING SYSTEM FOR RAILROADS 2 Sheets-Sheet 2 Filed June22, 1957 INVENTOR BY M m 'ToRNizY Patented May 2 1939 UNITED STATES PATENT OFFICE John I. Vaughn, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application June 22, 1937, Serial No. 149,702

12 Claims.

This invention relates to interlocking systems for railroads, and more particularly pertains to such systems automatically operated by the presence of trains on the track sections.

In accordance with this invention, a track layout having a railway crossing is provided with signals for governing traiiic in both directions over each track with the clearing of each signal initiated by the presence of a train on the approach section for that signal. As a means for allowing the signals for only one of the two conflicting tracks to clear at any one time, a neutral relay is provided for each of the two tracks, only oneof which can be effective to allow the clearing of its associated signals at the same time. Further, only one signal for each track can clear at any one time, inasmuch as each signal control is selected through front contacts on the track relay for the opposing approach track section for that track. In other words, if both approach track sections for a given track are occupied at the same time, neither train can clear a signal.

One of the features of the present invention is the use of an approach track section as a means for initiating the setting up of a route in such a manner as to prevent a train leaving the route thus set up from automatically setting up the route for the opposite direction. This is accomplished by the particular arrangement of track relays for the two opposite approach sections for each track. More specifically, the two track relays for each track have their armatures mechanically interlocked in such a manner that when 35 a train enters one approach section, the armature of the track relay for the other approach section is locked mechanically in a mid-position, so that its regular front contacts will be broken, and its regular back contacts will not be closed even while the train is passing through its associated section in leaving the plant. The fact that the back contacts are not closed prevents the setting up of a receding route, that is, a route in back of a train, such as to clear signal ll due to an east bound train passing out of section 5. Inasmuch as track relays are essential to any system of this kind, this system is particularly economical in providing this feature and no extra relays are required.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to the accompanying drawings in which like reference characters designate like apparatus and are made distinctive by means of preceding numerals.

Fig. 1 shows one embodiment of the present invention as applied to a railway crossing in which each track is signalled for traffic in both directions.

Fig. 2 shows a modification of the invention to make the invention adaptable to certain traffic conditions hereinafter disclosed.

With reference to Fig. 1, the track A is shown as having been divided into track sections 2, 3 and 5; and it is crossed by track B which is divided into track sections 8, l and 9. Track relays 2T, ST and ET are provided for their respective track sections, of which track relay ET and track relay 2T are mechanically interlocked. For the track sections 6, 1 and 9 on track B, track relays 6T, IT and ST are provided for their respective track sections and relays ST and ST are mechanically interlocked.

With reference to Fig. 2, the track A is shown as having been divided into track sections 2, 3, a and 5; and crossed. by track B which is divided into track sections 6, l, 8 and 9. A track relayis furnished for each track section; and track relay ET is mechanically interlocked with track relay 1T, track relay 2T is mechanically interlocked with track relay 3T, track relay 8T is mechanically interlocked with track relay HT, and track relay 4T is mechanically interlocked with track relay EST.

The track relays, which are mechanically interlocked, may be of any usual construction employed for mechanically interlocked relays so that their neutral armatures will be locked or held in mid-positions under certain operating conditions, as shown, for example, in the patent of O. S. Field, Patent No. 1,824,131 dated September 22, 1931. Such relays have not been shown in detail as it is believed sufiicient for an understanding of the present invention to know that when a first of two interlocked track relays drops its contacts, a dog on the mechanical interlock mechanism is actuated to a position which will allow the armature of the second interlocked track relay to drop only to a mid-position if said second relay drops before said first relay is again picked up. This locking condition for the second track relay is maintained effective, even if the first relay is re-energized, so long as the second relay remains deenergized. In other words, the dropping of either of the interlocked relays actuates the dogs of the mechanically interlocked mechanism in such a way as to allow the other interlocked relay to drop only half way, this interlocking feature being effective until said other track relay has again been energized, at which time the locking dogs return to their normal positions. The mechanical interlock is so arranged that if both relays were to be deenergized at the same time either one or the other of the relays would be locked in mid-position, that is, under no conditions can both relays be fully dropped away. These track relays for the approach sections are provided with make-before-break contacts so as to allow a circuit to be closed only when their relay armatures are in mid-positions.

The signals I3 and I I are associated with track A so as to control traffic in both directions, signal I0 governing east-bound traffic, and signal II governing west-bound trafiic. Trafiic over track B is controlled by signals I2 and I3 of which signal I2 governs east-bound traffic and signal I3 governs west-bound trafiic. The signals illustrated are of the search-light type, for example, as shown in the patent to O. S. Field, Patent No. 1,835,150 dated December 8, 1931. These signals are provided with a contact which is closed only when the vane of the mechanism is in its deenergized position so as to cause the signal to display a stop indication. Although search-light type signals are shown in describ ing this particular embodiment of the invention, it is to be understood that other types of signals may be used and the signal operated contact shown may be a contact on a signal controlling relay.

Associated with each track is a slow acting route control relay, relay AS having been provided for track A, and relay BS having been provided for track B.

A timing mechanism having normal and reverse contacts is provided for each track for the purpose of providing a means for releasing a route which has been set up, and causing a time interval under such conditions before a signal for a conflicting route can be cleared. The particular timing device shown is of the familiar screw release type, although it is to be understood that any suitable timing device could be used, providing it has normal contacts that open at a time interval before the reverse contacts are closed, and that the normal contacts are again closed at the end of the operation.

Instead of showing the detailed structural characteristics of the various devices employed in the embodiment of. the invention various symbols have been used to represent these devices, the drawings having been made more with the purpose of facilitating the disclosure with reference to the mode of operation. Thus, the various relays and their controls are illustrated in a conventional manner and symbols are used to indicate connections to suitable battery supply.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries.

It is believed that the features of the present invention will best be understood by consideration of the operation under various typical conditions.

Operation With reference to Fig. 1 it is obvious that the track relays are all in their energized positions under normal conditions. Under these conditions the signals are all in a position to indicate stop, and the route control relays AS and BS are in their energized positions.

Relay AS is energized from through a circuit including contact 20 of signal I0, contact 2| of signal II, normal contact 22 of time release AMX, front contact 23 of relay BS, front contact 24 of relay 2T, front contact 25 of relay 5T, and winding of relay AS, to

Relay BS is energized from through a circuit including contact 26 of signal I2, contact 2! of signal I3, normal contact 28 of time release BMX, front contact 29 of relay AS, front contact 30 of relay 9T, front contact 3| of relay BT and winding of relay BS, to

The track relays 2T and ST are deenergized whenever the track sections 3 or I are occupied respectively. The reason for this particular arrangement isto keep the track relay for the approach section at the leaving end of the interlocking plant at locked position so as to prevent the setting up of a receding route. This will be more clearly understood after considering the operation during the passage of a train. Relay 2T is energized from through a circuit including south rail of track section 2, front contact 32 of relay 3T, winding of relay 2T and north rail of track section 2, to Track relay ST is energized from through a circuit including south rail of track section 9, front contact 33 of relay IT, winding of relay QT, and north rail of track section, to

Assume a train to approach signal I0 on track A so as to occupy approach track section 2 and drop relay 2T. When relay 2T drops the control of relay AS is opened at front contact 24.

When relay AS drops the stick circuit for relay BS is closed so as to prevent the dropping of that relay by a train which may enter either of the approach sections on track B. Relay BS is then energized from through a circuit in-- cluding contact 26 of signal I2, contact 27 of signal I3, normal contact 28 of time release BMX, back contact 29 of relay AS, front contact 54 of relay BS and winding of relay BS, to

A circuit is now closed for energizing the mechanism of signal II] from through a circuit including contact 26 of signal I2, contact 21 of signal I3, normal contact 28 of time release BMX, back contact 35 of relay AS, front contact 36 of relay 3T, normal contact 31 of time release AMX, front contact 38 of relay IT, front contact 39 of relay BS, front contact 40 of relay 5T, and back contact 4| of relay 2T, to the control of the mechanism of signal I0. When energy is applied to the signal mechanism the vane carrying the red and green spectacle is caused to operate into such a position as to cause the beam of light emitted from the signal to pass through the green spectacle rather than the red spectacle.

It will be noted that the control of signal I0 is broken through contacts on signals I2 and I3, which contacts are closed when the signal is at stop so as to directly check the stop position of the signals on the conflicting track. It will also be noted that before signal I0 could clear, stick relay BS Was proved to be stuck in its energized position by reason of the signal control having been selected through front contact 39 of relay BS. This particular arrangement of the circuit insures the sticking of the relay for the conflicting track so as to prevent that relay from becoming deenergized when a train enters either of the approach track sections for that track.

When the train accepts signal I0 and drops track relay 3T the control of the signal mechanism is opened at contact 36, thus allowing the vane in 'the' signal mechanism to drop to a position which will cause the beam of light to pass through the red spectacle.

It will be noted that inasmuch as relays 2T and Tare mechanically interlocked in a manner previously described, the dropping of relay 2T actuated a locking dog so as to allow the armature of relay 5T to drop only to the locked position. When track relay 3T drops, the circuit for the control of relay ET is opened at front contact 32 and a shunt is placed across the relay winding byreas'on of back contact 32 becoming closed. This provides a means for holding said locking dog in position until relay-5T drops.

1 When the train enters the track section 5 and drops relay 5T, bearing in mind that contact M! is locked against making up its back contact, a circuit is closed for picking up relay AS from through a circuit including contact 2!] of signal l0, contact 2i of signal ll, normal contact 22 of time release AMX, front contact 23 of relay BS, front make-before-break contact 42 of relay 5T, back make-before-break contact 42 of relay 5T, back contact 43 of relay ST and winding of relay AS, to When relay AS picks up a stick circuit is closed through front contact 34 so as to shunt out back contact A3 of relay 3T through a circuit including wire 44. This provides a means for retaining relay AS in its energized position after the train leaves track section 3.

Whenthe train leaves track section 3, the picking up of relay 3T allows a circuit to be closed at front contact 32 for picking up relay 2T, but it will be noted, however, that relay 5T remains in its locked position even though relay ET is energized, due to the particular arrangement of the locking dogs. .After the train leaves track section 5 and track relay 5T picks up, the locking dogs will drop back to their normal position due to both interlocked relays having become energized.

When both approach track relays 5T and TI have become energized, the normal energizing circuit for relay AS is again closed at contacts 25 and 24 respectively. This returns the relays to their normal positions and the interlocking plant is again in condition to be operated by a second approaching train. 7

Assume the second approachingtrain to approach signal E2 on track B and drop relay 6T. When relay 6T drops, the control of relay BS is opened at front contact 3 l and when this relay drops the stick circuit is closed for relay AS from through a circuit including contact 26] of signal l0, contact 2! of signal ll, normal contact 22 of time release AlVIX, back contact 23 of relay BS, front contact 3 of relay AS and winding of relay AS, to 7 'A circuit is closed for energizing the mechanism of signal l2 from through a circuit including contact 25 of signal H3, contact 2! of signal H, normal contact 22 of time release AMX, back contact 45 of relay BS, front contact 66 of relay lT, normal contact 41 of time release BMX, front contact 38 of relay 3T, front contact 49 of relay AS, front contact 59 of relay QT, and back contact 5| of relay 6T, to the mechanism of signal l2. When the mechanism becomes energized, the vane carrying the spectacles is caused to rotate to such a position as to cause the beam of light emitted from the signal to pass through the green spectacle.

When the train accepts signal lZand enters track-section v 1, thes dropping of; relay 1T causes the deenergization: of relay 9T by reason of the opening of. frontcontact 33, and also causes a shuntito :be applied across .the winding of relay ST'by reason of theclosing of back contact 33. 'When relay ,QT; drops it drops only to its midpos'ition due to .relayiiT having been dropped pIeViOLlSlYISO as to lock the armature of relay 9T. The vane of themechanism of signal i2 is allowed to drop, due to the opening of contact it of relay .lT, so as to substitute the red spectacle .for the green spectacle in alinement with the beam of light? emittedfrom the signal due to the opening -'of front contact 46 of relay 'FT.

When track relay 9T drops, a circuit is closed for energizing relay BS from through a circuit including contact 2.6 of signal I2, contact 27 of signal-13,.normal contact 28 of time release BMX, ifront contact 23 of relay AS, front makebefore-break contact. 52 of relay 9T, back makebefore-breakcontact 52 of relay 9T, back contact 5301. relay IT and winding of relay BS, to Astickcircuit-is closed through front contact fi i'of relay BS so as to shunt out back contact 5310f relaylT through a circuit including wire 55. 1

As'the train leaves track section i, relay BS is held in its energized position by reason of the stick circuit. just described.

When the train leaves track section 9, the nor- .mal energizingcircuit'for relay BS is closed, due to relays fiTlancl 9T having been returned to their energized positions. The locking dogs for relay GT and 9T have again returned to their normal positions by reasonof both relays having become energized.

Provision is-rnade for the emergency release of a route setiup oneither track so as to give the train on'the other track preference by operation of. the time" release for the track on which the preference is desired. Furthermore, after the time relea'se has been operated so as to releasebne routeancl set up. a second route, the second route may as well be released andv the first route againv set up without either train having entered the interlocked limits.

' To illustrate the operation of the time release,

Jassumea train to approach signal if? on track A erate the time release BMX so as to open the normal contacts, close'the reverse contacts, open the reversecontact's, and again close the normal contacts, before signal l2 can be cleared. When the time release BlVlX is operated from its normal position the control of signal I 0 and relay BS are opened at' 'normal contact 28 of time release BMX; When the time release is operated to its reverse-position, a circuit is closed for energize ing relay AS from through a circuit including contact 20 of signal l0, contact 2| of signal ll, normal' contactZZ-Qf the time'release AMX, reversecontact 55 of: time release BlVlX and windin of relay AS, to When this relay becomes energized a stick circuit is closed from through acircuit.ihcluclingcontact 20 of signal Ill, contact 2d of signalzl [,normal contact 22 of time release AMXgbackcontact 23 of relay BS, front contact 340i relay AS, and winding of relay AS,.to,(.- .i .1

When relay AS is energized the stick circuit for relay BS is opened at back contact 29. As soon as the time release BMX has again closed its normal contacts a circuit is closed for energizing the mechanism of signal I2 from through a circuit including contact 20 of signal I0, contact 2i of signal II, normal contact 22 of time release AMX, back contact 45 of relay BS, front contact it of relay l'T, normal contact 41 of time release BMX, front contact 48 of relay 3T, front contact 49 of relay AS, front contact 50 of relay 9T, back contact 5I of relay 6T, to the mechanism of signal IZ. The energization of the signal mechanism causes the red spectacle to be replaced by the green spectacle in alinement with the beam of light emitted from the signal so as to give the train approaching signal I2 a clear indication.

It is obvious that the operation of the time release AMX for causing signal 12 to go to stop so asto allow signal II] to clear requires the same mode of operation as that described above.

By reason of the particular arrangement of the control of the relays AS and BS alternate moves are provided under traffic conditions where the approach sections on the two conflicting tracks become occupied before a train has left the opposing approach section. For example, assume a train to have approached and accepted signal I0 on track A, so as to have entered the interlocking limits. Then assume a following train to approach signal I0, and also a short time later a train to approach signal I2 on track B so as to drop track relay 6T. Although the train on track B may have been later in entering the approach section for signal I2 than the following train on track A was to enter the approach section for signal IS, the train on track B will receive preference over the following train on track A.

The means for selecting the alternate moves is provided in the fact that relay AS sticks up when the make-before-break contacts 42 of track relay ET are closed. When relay AS picks up the stick circuit for relay BS is broken at back contact 29 so as to cause relay BS to drop, due to its normal control being open at contact 3| of relay 6T.

The relays have therefore been positioned for setting up a route for the train on track B and signal I? will clear as soon as the first train on track A has left track section 3 and relay 3T has become energized so as to close the signal control at contact 48.

Inasmuch as the apparatus and controls for each track are similar, it is of course obvious that alternate moves will be selected, providing that following trains approach on tracks A and B after the first train on track B has accepted signal I2.

Having thus described in detail the control of signals ill and I2 under various traffic conditions, it is to be assumed that similar operation is provided with trains approaching signals II and I3 under similar traffic conditions, inasmuch as the same circuits are employed, the only difference being the selection of the signals through the front and back contacts of the track relays for the approach sections.

The particular system described with reference to Fig.1 is, however, not adaptable to conditions where ,a switching move is liable to drop a track relay for one of the approach sections but yet not complete a move through the interlocking plant.

t is obvious that this condition, using interlocked relays as has just been described, would look up the plant so as to prevent a train which might approach on the same track from the other direction, from causing a route to be set up after the switching train has left the opposing approach section, due to the fact that the approach track relay for the approach section occupied by the second train has been locked in its mid-position by the presence of the first train on the opposing approach section. This condition has been overcome by providing separate track circuits for each track for each side of the crossing so as not to require the track relays for the two approach sections on one track to be mechanically interlocked. The track relays are, however, so interlooked as to effect the same mode of operation as was shown and described in detail for Fig. 1. Inasmuch as the mode of operation as shown in Fig. 2 is similar to that shown in Fig. 1, various details of the operation will not be repeated.

Under normal conditions, with reference to Fig. 2, relay BS is energizedfrom through a circuit including contact 5'! of signal I2, contact 58 of signal I3, normal contact 59 of time release BMX, front contact 55 of relay AS, front contact 6! of relay 6T, front contact 62 of relay ET and winding of relay ES, to

Relay AS is normally energized from through a circuit including contact 63 of signal l5, contact iii of signal it, normal contact 65 of time release AMX, front contact 66 of relay BS, front contact El of relay 5T, front contact 68 of relay ET and winding of relay AS, to

Assume a train to approach signal If! on track A so as to drop track relay ET and cause the deenergization of r lay AS due to opening its control at front contact 68. With relay AS down a stick circuit is closed for holding relay BS in its energized position from through a circuit including contact 5'! of signal I2, contact 58 of signal l3, normal contact 59 of time release BMX, back contact 66 of relay AS, front contact 69 of relay BS and winding of relay BS, to

A circuit is closed for energizing the mechanism of signal Ill from through a circuit including contact 5'! of signal !2, contact 58 of signal I3, normal contact 59 of time release BMX, back contact 18 of relay AS, front contact II of relay IT, front contact l2 of relay 3T, normal contact 13 of time release AMX, front contact M of track relay 8T, front contact I5 of track relay 4T, front contact "I6 of relay BS, front contact 1'! of relay 5T and back contact I8 of relay 2T to the mechanism of signal Ill. The energization of the signal mechanism of course causes the red signal indication to be replaced by the green indication in a similar manner to that previously described with reference to Fig. 1.

After the train accepts the signal, the signal control is opened at contact l2 of relay 3T so as to cause its indication to be at stop, and the entrance of the train into block 5 causes relay AS to again be energized from through a circuit including contact 63 of signal l0, contact 64 of signal 5 i, normal, contact 65 of time release AMX, front contact 55 of relay BS, front makebefore-break contact 19 of relay 5T, back makebefore-break contact I9 of relay 5T, back contact 80 of relay 4'1, and winding of relay AS, to When the relay becomes energized a stick circuit is closed through front contact III of relay AS so as to shunt out the back contact 86 of relay 4T.

The picking up of relay AS closed the normal energizing circuit for relay BS at front contact 65!, and as soon as the train leaves track section 5 the interlocking plant is again returned to its normal conditions.

The particular feature of this modification of the invention is to provide means of isolating the opposite approach sections on each track from each other as far as the mechanical locking of their relay armatures is concerned. For example, assume a train to have entered track section 5, with-no intentions of proceeding through. the plant, so as to drop track relay ST, and a short time later assume a train to have entered track section 2 on the same track with the desire of proceeding through the interlocking plant as soon as the-train on approach section 5 has left that track section. It isobvious that under this traiflc condition there is nothing to prevent the route for the second train on track A from being cleared in the usual manner as soon as the train which occupies track section 5 has left that section.

The reason for the pick up circuit of relays AS having been taken through the back contact 80- of relay 5T in series with the front and back make-before-break contacts 19 of the approach track relay ST is to provide greater protection against a shunt releasing a clear signal in the face of an approaching train and allowing a conflicting route on. the other track to be set up by an approaching train on that track. For example, assume a train to approach signal Ill on track A so as to receive a clear signal. If for some reason or other, either of the track relays 4T or 5T should become deenergized, the relay AS would pick up, thus causing signal it to go to stop and allowing a signal for the conflicting track, such as might be signal l2 with a train approaching on track B, to be cleared, providing that relay AS were energized through either of the back contacts of track relays 4T or ET. The present circuit arrangement, however, provides that relay AS is energized only when track relays QT and 5T are deenergized' in the particular order mentioned. This provides that a signal for the conflicting track cannot be cleared under conditions mentioned above unless both of the track relays AT and 5T have been dropped in the order mentioned. This is a condition which would of course not be very liable to happen.

Having thus described specific features of "this invention with regard to track A, it is to be assumed that similar operation for track B is effective under similar traffic conditions.

Summary.

Some of the particular features which have" special relays for accomplishing this purpose.

The signal control circuits for one track include contacts on the mechanism of the signals for the conflicting track so as to provide a'positive" check that such conflicting signals are at stop before'a signal for said one track is cleared.

An emergency release is provided for each track in such a manner that a route once released on one trackmay again be restored by the operation of the other emergency release without requiring either train to haveaccepted the route which was previously setup for it.

Means has been provided by the particular arrangement of the controlof the AS and BS relays so as to providefor train movements over the two tracks alternately at times when following trains occupy approach sections on both tracks before a preceding train has left the interlocking plant.

Protection has been provided against returning to stopv a route set up for one train and immediately clearing a route on the conflicting track for another train as a result of the abnormal dropping of the track relays for either of the track sections in advance of the first train.

The arrangement of the circuits is such that the stick circuit for the stick relay for onetrack is proved to be intact before a signal is cleared for a train on the other track.

Having described a'railway crossing as one specific embodiment of the present invention, it is desired to be understood that this form is selected only to facilitate in the disclosure of the invention rather than to limit the number of forms which it may assume; and, it is to be further understood that various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention except as limited by the appended claims- What I claim is: 1. In a trafflc controlling system for railroads, a track layout having a plurality of conflicting routes, signals for governing trafiic in both direc tions over each route, an approach track section for each signal, circuit means for causing each signal to clear when its respective approach section is occupied, circuit meansfor allowing only relay associated therewith for each signal, circuit means for causing each signal to clear when the approach track section for that signal is occupied, automatically controlled means for allow: ing the armature of either of said track relays for each track to drop only partway, providing the armature of the track relay for the otherapproa ch track section is dropped all of the way, circuit means for causing a signal to be cleared only when the armature of the track relay for its respective approach track section is dropped all of the way, and circuit-means for allowing only one signal to clear at any one time.

3. In a traffic controlling system for railroads; a track layout having a plurality of conflicting routes; signals for governing traflic over each route in both directions; an approach track section having a track relay associated therewith for each signal; automatically controlled means dependent on the operation of a first approach track relay for allowing the dropping of the armature of a second approach track relay for the same track to a mid-position only by a train leaving the interlocking plant; and circuit means for causing a signal to clear when its respective approach section is occupied, providingthat the armature of the track relay for that approach signal is allowed to drop all of the way, and providing that all conflicting signals are at stop.

4. In a traffic controllingsystem for railroads, a track layout having a first stretch of track crossed by a second stretch of track, signals for governing traflic over each track, an approach track section for each signal, a neutral relay for each track, circuit means for energizing each of said relays when the signals for their respective tracks are at stop, circuit means for causing either of said relays to be deenergized when an approach section for that track is occupied, circuit means whereby when either one of said neutral relays is deenergized, the other neutral relay cannot-becomedeenergized, and circuit means for causing a signal to clear for each track only when said relay for that track is deenergized and said relay for the other track is energized.

5. In a trafiic controlling system for railroads, a track layout having a plurality of conflicting routes, signals for governing trafllc over each route, an approach track section having a track relay associated therewith for each signal, circuit means for causing a signal to clear when a train occupies its respective approach section, and mechanically interlocked contact means on said track relays for allowing only one of all opposing signals on the same track to clear at any one time.

6. In a trafilccontrolling system for railroads, a track layout having a plurality of conflicting routes, signals for governing traflic over each route, an approach track sectionhaving a track relay associated therewith for each signal, circuit means for clearing each signal when a train occupies the approach track section for that signal, a'neutral relay for each track, circuit means for energizing each of said neutral relays and for causing each of said neutral relays to be deenergized when a train occupies an approach track section for that track, circuit means responsive to the operation of said neutral relays for allowing signals on only one of all confiicting tracks to clear at any one time, and means responsive to the operation of said track relays for each track for allowing only one of all. conflicting signals on that track to clear at any one time. e

7. In a trafiic controllingsystem for railroads, a track layout having a first stretch of track crossed by a second stretch of track, signals for governing trafiic over each track in each direction, an approach track section'having a track relay associated therewith for each signaL circuit means responsive to the operation of said track relays for allowing only one signal onthat track to clear at any one time, a neutral relay for each track, circuit means for energizing each of said neutral relays and for causing each of said neutral relays to be deenergized when an approach track section for that track is occupied, circuit means for causing each of said neutral relays to be reenergized during occupancy by a receding train of the other approach track section for that track, circuit means responsive tothe operation of said neutral relays for causing signals on each track to clear and responsive to the operation of said neutral'relays for allowing signals on only one of all conflicting tracks to clear at any one time, and means dependent upon the operation of said neutral relays, and involving the control by occupancy of the approach sections by entering and leaving trains, and the means for allowing signals on only one of-all conflicting tracks to clear, for automatically clearing a signal first on one track and then on the other track as long as approach track sections on both tracks are occupied by approaching trains before a preceding train has left the opposing approach tracksection.

8. In a traffic controlling system for railroads; a track layout having a first stretch of track crossed by a second stretch of track; signals for governing trafiic over each stretch of track; an approach track section having a track relay associated therewith for each signal; circuit means for causing each signal to clear when a train occupies the approach track section for that signal; circuit means responsive to the operation of said track relays for allowing only one signal on each track to clear at any one time; a neutral relay for each track; circuit means for energizing each of said neutral relays; circuit means for causing each of said neutral relays to be deenergized when a train occupies an approach track section for that track; circuit means responsive to the operation of said neutral relays for allowing signals on only one track to clear at any one time; a time contactor for each track; and circuit means responsive to the operation of said contactor on each track for causing a signal on that track to change its indication from clear to stop and for allowing a signal on the other track to be cleared only at the end of a predetermined time interval.

9. In a traflic controlling system for railroads, a track layout having a first stretch of track crossed by a second stretch of track, signals for governing traffic over each track, an approach track section for each signal, circuit means for causing each signal to clear when its respective approach section is occupied by an approaching train, a neutral relay for each track, circuit means for energizing said neutral relay, circuit means for causing said neutral relay to be deenergized-when an approach track section for that track is occupied, circuit means for allowing the signals for only one track" to clear at any one time, and means for preventing the clearing of a signal for one track providing a signal on the other track has changed its indication from clear to stop, due to the dropping of a track re-c lay in advance of the signal on said other track.

10. In a trafiic controlling system for railroads, a track layout having a first stretch of track crossed by a second stretch of track, signals for governing trafiic over each track, an approach track section having a track relay associated therewith for each signal, circuit means for clearing each of said signals when an approaching train occupies its respective approach track section,a neutral relay for each track, circuit means for energizing each of said. neutral relays and for deenergizing each of said relays when a train occupies an approach section for that track, circuit means for preventing the energization of signals on more than one track at any one time, means dependent uponthe operation of said track relays for allowing only one signal on each track to clear at any one time, and means included in the control circuit of each signal for checking I the position of the signal mechanism of the signals for the conflicting track.

11. In a trafiic controlling system for railroads, in combination; a track layout having a first stretch of track crossed by a second stretch oi track; an approach track section including a track relay for each end of each track stretch; an intermediate track section including a track relay for each stretch; a signal at each end of each stretch of track; means interlocking the track relays of the two approach sections for each of the stretches, so that when one is released, the other is latched against release until after the one is picked up and then the other is energized, and an energizing circuit for each signal effective only if its associated interlocked track relay is in released position.

12. In a trafiic controlling system for railroads, in combination; a track layout having a first stretch of track crossed by a second stretch of track; an approach track section including a track relay for each end of each track stretch; an intermediate track section including a track relay for each stretch; a signal at each end of each stretch of track; means interlocking the track relays of the two approach sections for each of the stretches, the interlock operating, in the case of each pair of relays, when one is deenergized, to prevent the other, even though deenergized, with a usual contact, from making up its back point until after it has again been energized following the reenergization of the said one relay, each relay having a make-before-break contact, which, when the relay is locked and deenergized, makes up both its front and back point; and circuit means including the interlocked relays and their make-before-break contacts, for governing the signals.

. JOHN I. VAUGHN. 

